Weather radar observations of the Hekla 2000 eruption cloud, Iceland

摘要: The Hekla eruption cloud on 26–27 February 2000 was the first volcanic to be continuously and completely monitored advecting above Iceland, using C-band weather radar near Keflavik international airport. Real-time observations of onset, advection, waning were studied time series PPI (plan-position indicator) images, including VMI normal, Echotop, Cappi level 2 displays. reflectivity entire ranges from 0 >60 dBz. column vent is essentially characterised by normal values, >30 dBz, due dominant influence lapilli ash (tephra) overall reflected signal. generated advected downwind north-northeast. It values between 30 persistence these reflections likely result continuing water condensation freezing particles. Echotop images onset document a rapid ascent plume head with mean velocity ~30 50 m s−1, before it reached an altitude ~11–12 km. evolution area change in pixels its highly portions, tied recorded tremor amplitudes. synchronous initial variation both seismic signals documents abrupt increase tephra emission magma discharge rate 18:20 19:00 UTC 26 February. From >45 dBz 30–45 portions decrease disappear at about 7 10.5 h, respectively, after began, indicating end decaying explosive phase. advection extent compared eyewitness accounts fall measured mass deposited ground during 12 h. Differences deposit map are fact that greater part originates fallout off margins base followed falling particle lower winds.